The present invention relates to a changer which transports one of many housed information recording media (for example, disks) that is designated by a computer system, to a designated one of plural incorporated information recording medium driving means (for example, disk drives), thereby enabling the computer system to rapidly access any one of the many housed information recording media, and particularly to a changer which can incorporate information recording medium driving means in a larger number (for example, sixteen) than the maximum number of devices that can be supported by one SCSI bus.
As a device for providing rapidly and accurately only required information among an enormous quantity of information stored in many information recording media (for example, disks such as CD-ROMs, CD-Rs, DVD-ROMs, DVD-Rs) to a computer system, conventionally, known is a changer configured in the following manner. Among many housed disks, a disk which is designated by the computer system is transported to designated one of plural incorporated disk drives, so that the computer system can access any one of the many housed disks.
FIG. 10 schematically shows a usual electrical hardware configuration of an example of a changer of the conventional art, and connection relationships between the changer and a computer system. As shown in the figure, the changer 1 incorporates a changer controller 2 which mainly controls transportation of disks, and four disk drives 31 to 34 which are mounted at positions identified by a series of element addresses (EA) and serve as transport destinations of the disks, respectively.
The computer system 6 is connected to each of elements (the changer controller 2 and the disk drives 31 to 34) of the changer 1 via a SCSI (an abbreviation for Small Computer System Interface) bus. Eight SCSI controllers respectively corresponding to SCSI IDs=0 to 7 can be connected to a SCSI bus of an 8-bit width. In this example, a SCSI controller (host adapter) 47 corresponding to SCSI ID=7 is connected to the computer system 6, a SCSI controller 45 corresponding to SCSI ID=5 is connected to the changer controller 2, and SCSI controllers 41 to 44 corresponding to SCSI IDs=1 to 4 are connected to the four disk drives 31 to 34, respectively. There are no SCSI controllers corresponding to SCSI IDs=0 and 6.
In the changer 1, between the changer controller 2 and device connectors (not shown) corresponding to the element addresses (EA), a local bus line 5 elongates through which drive identification data are sucked from a disk drive connected to the connector, to the changer controller 2. In this example, as the drive identification data, the SCSI IDs (IDs=1 to 4) allocated to the SCSI controller to which the disk drive are connected is used as they are, because, when there is only one SCSI bus, the SCSI IDs correspond to the disk drives in one to one relationship. The SCSI IDs can be respectively set for the SCSI controllers by using a DIP switch or the like. As required, the SCSI IDs can be read from the side of the disk drives. The SCSI IDs set by the DIP switch or the like are used also for enabling the computer system 6 to access a desired one of the disk drives via the corresponding SCSI controller.
In order to enable the computer system 6 to read desired data from one of the disks housed in the disk changer 1, instructions for transporting the disk to one of the disk drives 31 to 34, and also those for controlling the disk drive serving as the transport destination of the disk and reading the desired data from the transported disk must be given from the computer system 6 to the disk changer 1. These instructions are given by issuing predetermined commands (hereinafter, such commands are referred to as xe2x80x9cdisk transportation command,xe2x80x9d and xe2x80x9cdisk access command,xe2x80x9d respectively) onto the SCSI bus from the computer system 6 while designating the corresponding SCSI ID.
Specifically, the instructions for transporting a specific disk to one of the disk drives 31 to 34 are performed in the following manner. The computer system 6 issues the disk transportation command (containing designation of the disk) onto the SCSI bus while designating the SCSI ID (ID=5) allocated to the SCSI controller 45 to which the changer controller 2 is connected. At this time, in the designation of the disk drive of transport destination, the element address EA allocated for specifying the disk drive in the changer is used in place of the SCSI ID of the SCSI controller to which the disk drive is connected. This is specified in the SCSI standard. In the disk transportation control performed by the changer controller 2, it is necessary and sufficient that only the changer controller 2 recognizes the physical position of a disk drive to which a disk is to be transported. Therefore, the element address EA having a one to one relationship with the physical position of the disk drive is used as a logical address.
By contrast, the instructions for controlling the disk drive positioned at the transport destination of the disk and reading the desired data from the disk set to the disk drive are performed in the following manner. The computer system 6 issues the disk access command onto the SCSI bus while designating the SCSI ID allocated to the SCSI controller to which the transport destination disk drive is connected.
In the changer 1, correspondence relationships between SCSI IDs for recognizing the disk drives and the element addresses EA given to the disk drives are not uniquely defined. When the disk transportation command and the disk access command are to be issued, therefore, the computer system 6 must previously recognize correspondence relationships in the changer 1, i.e., those between the SCSI ID for identifying a disk drive and the element address EA indicating the position where the disk drive is mounted. The correspondence relationships are recognized by the computer system 6 in the following procedure.
Prior to the disk transportation control, first, the changer controller 2 acquires the SCSI IDs serving as drive identification data from the four incorporated disk drives 31 to 34 via the local bus line 5, and recognizes correspondence relationships between the element addresses EA and the disk drives (SCSI IDs). The acquisition of the SCSI IDs by the changer controller 2 can be performed in any one of various know methods. In this example, the changer controller 2 first performs an initializing process immediately after power-on, or issues a predetermined internal request command via the local bus line 5 to each of the four incorporated disk drives 31 to 34 which are incorporated in the changer and which can be respectively designated by the corresponding element address. In response to the command, the disk drives 31 to 34 read the SCSI IDs (=1 to 4) from their own SCSI controllers 41 to 44, respectively, and send the SCSI IDs to the changer controller 2 via the local bus line 5. When the changer controller 2 receives the SCSI IDs, the changer controller recognizes correspondence relationships between the SCSI IDs of the disk drives 31 to 34 and the element addresses. In FIG. 11A, an example of the thus recognized correspondence relationships is shown in the form of a table. As seen from the table, in the example, it is recognized that the four disk drives 31 to 34 are mounted at positions indicated by element addresses EA=4000 to 4003, and the SCSI IDs of the disk drives 31 to 34 are 1 to 4, respectively.
In order to correctly issue various commands to the elements (the changer controller 2 and the disk drives 31 to 34) of the changer 1, the computer system 6 must previously know the manner of connecting the elements to the SCSI bus. Prior to the start of the control, therefore, the computer system 6 sequentially issues an inquiry command to all the SCSI IDs (=0 to 7), and, on the basis of device types which are sent from the SCSI controllers in response to the command, recognizes correspondence relationships between the SCSI IDs and the device types. In FIG. 11B, the thus recognized correspondence relationships between the SCSI IDs and the device types are shown in the form of a table. As seen from the table, according to the correspondence relationships, it will be seen that the changer controller 2 is connected to the SCSI controller corresponding to the SCSI ID=5.
The computer system 6 acquires the correspondence relationships of FIG. 11A which have been recognized by the changer controller 2, as they are to recognize the correspondence relationships between the SCSI IDs for identifying the disk drives and the element addresses EA indicating the mounting positions of the disk drives. This recognition is performed in the following procedure. First, the computer system 6 issues a read element status command which is defined in the SCSI standard, while designating the SCSI ID (ID=5) allocated to the SCSI controller 45 to which the changer controller 2 is connected. In response to the command, the changer controller 2 sends the recognized correspondence relationships onto the SCSI bus, while designating the SCSI ID (ID=7) allocated to the command source. When the computer system 6 acquires the reply, the computer system recognizes the correspondence relationships between the SCSI ID for identifying the disk drive and the element address EA indicating the mounting position of the disk drive.
In a large changer such as that which can incorporate sixteen disk drives at the maximum, depending on the number of incorporated drives, there may arise a case where the drives cannot be supported by one SCSI bus because of the restriction that the maximum number of devices which can be connected to one SCSI bus of a 8-bit width is eight.
FIG. 12 schematically shows the electrical hardware configuration of a large changer incorporating sixteen disk drives, and connection relationships between the changer and a computer system. As shown in the figure, the changer 10 incorporates a changer controller 20 which mainly controls transportation of disks, and sixteen disk drives 301 to 316 which are mounted at positions identified by a series of element addresses (EA) and serve as transport destinations of the disks, respectively.
The computer system 60 is connected to elements (the changer controller 20 and the disk drives 301 to 316) of the changer 10 via three SCSI buses of an 8-bit width which are respectively identified by SCSI bus numbers #1 to #3. Eight SCSI controllers corresponding to SCSI IDs=0 to 7 can be connected to each of the three illustrated SCSI busses. In this example, with respect to SCSI bus #1, a SCSI controller (host adapter) 147 corresponding to SCSI ID=7 is connected to the computer system 60, a SCSI controller 145 corresponding to SCSI ID=5 is connected to the changer controller 20, and SCSI controllers 140 and 141 corresponding to SCSI IDs=0 and 1 are connected to two disk drives 301 and 302, respectively. There are no SCSI controllers corresponding to SCSI IDs=2, 3, 4, and 6. With respect to SCSI bus #2, a SCSI controller (host adapter) 247 corresponding to SCSI ID=7 is connected to the computer system 60, and SCSI controllers 240 to 246 corresponding to SCSI IDs=0 to 6 are connected to seven disk drives 303 to 309, respectively. With respect to SCSI bus #3, a SCSI controller (host adapter) 347 corresponding to SCSI ID=7 is connected to the computer system 60, and SCSI controllers 340 to 346 corresponding to SCSI IDs=0 to 6 are connected to seven disk drives 310 to 316, respectively.
In the changer 10, between the changer controller 20 and device connectors (not shown) corresponding to the element addresses (EA), a local bus line 50 elongates through which drive identification data are sucked from a disk drive connected to the connector, to the changer controller 20. In this example also, as the drive identification data, the SCSI IDs (IDs 0 to 7) allocated to the SCSI controllers to which the disk drive is connected are used as they are.
In the large changer 10 also, prior to the control of disk transportation, the changer controller 20 acquires the SCSI IDs serving as drive identification data from the sixteen incorporated disk drives 301 to 316 via the local bus line 50, and recognizes correspondence relationships between the element addresses EA and the disk drives (SCSI IDs). In FIG. 13, the thus recognized correspondence relationships are shown in the form of a table.
Prior to the start of the control, the computer system 60 sequentially issues an inquiry command to all the SCSI IDs (=0 to 7) of SCSI buses #1 to #3, and, on the basis of device types which are sent from the SCSI controllers in response to the command, recognizes correspondence relationships between the SCSI bus numbers, the SCSI IDs, and the device types. In FIG. 14, the thus recognized correspondence relationships between the SCSI IDs for the SCSI bus numbers, and the device types are shown in the form of a table.
The computer system 60 recognizes the SCSI bus number and the SCSI ID of the changer controller 20 from the correspondence relationships shown in the table of FIG. 14, and then issues a read element status command, thereby acquiring and recognizing the correspondence relationships between the element addresses EA and the disk drives (SCSI IDs) listed in the table of FIG. 13.
At this time, the contents of information for recognizing the correspondence relationships which are acquired finally by the computer system 60 produce a problem. As seen from the table of FIG. 13, in response to the internal request command, each of the disk drives of the element addresses (EA=4000 to 4015) sends to the changer controller 20 a reply the content of which coincides with the SCSI ID read from the SCSI controller connected to the disk drive. When two or more SCSI busses are used as in the case of the changer, therefore, the identical SCSI IDs appear although the element addresses EA are different from each other, so that the SCSI buses to which the SCSI IDs belong cannot be identified. As a result, there arises a problem in that it is impossible to, from an element address EA, identify the electrical connection route (access path) to the disk drive mounted at the address, via the SCSI. For example, the following case will be considered. The disk transportation command is issued and a disk is transported to an element address (EA=4001). Even when, while referring to the correspondence relationships shown in the table of FIG. 13, the computer system thereafter issues the disk access command to the transport destination disk drive to try to access the disk drive, it is known, from the table of FIG. 13, only that the element corresponding EA=4001 is a disk drive identified by SCSI ID=1. In other words, the SCSI bus to which the SCSI ID=1 belongs cannot be known. As a result, a necessary command cannot be correctly issued to the transport destination disk drive.
The invention has been conducted in view of the above discussed problem. It is an object of the invention to, in a changer wherein a computer system accesses disk drives by using two or more SCSI busses in such a case where disk drives are incorporated in a larger number than the maximum number of devices that can be supported by one SCSI bus, enable the computer system to correctly recognize correspondence relationships between the disk drives and element addresses where the disk drives are mounted.
In a first aspect of the invention, a changer comprising: a changer controller which controls transportation of an information recording medium; and information recording medium driving means mounted at a position indicated by an element address and serving as a transport destination of an information recording medium, and, in the changer, the changer controller includes first controlling means for recognizing correspondence relationships between identifiers respectively peculiar to incorporated information recording medium driving means and element addresses, and for, in response to a first command, sending information relating to the correspondence relationships between the identifiers and the element addresses, to a source of the command, and each of the information recording medium driving means includes second controlling means for, in response to a second command, sending the identifier, to a source of the command.
According to this configuration, the changer controller recognizes correspondence relationships between identifiers respectively peculiar to the incorporated information recording medium driving means and the element addresses, and, in response to arrival of the first command, the recognized correspondence relationships are sent to a source of the command (for example, a computer system). Furthermore, in response to arrival of the second command, also each of the information recording medium driving means sends the identifier to the command source (for example, the computer system). In the command source (for example, the computer system), therefore, the element addresses or logical addresses of the information recording medium driving means are related to the electric connection routes (access paths) in one to one relationship, on the basis of a peculiar identifier which is commonly contained in both sets of information respectively obtained through the two routes. Consequently, the computer system can directly control the information recording medium driving means mounted on the changer.
In a second aspect of the invention, the identifier is previously recorded in the information recording medium driving means, and the first controlling means acquires the identifier from incorporated information recording medium driving means, to recognize the correspondence relationship between the identifier and the element address. This configuration can attain the following effects in addition to the effects of the first aspect of the invention. The identifier sent to the changer control or the computer system is stored in a nonvolatile memory such as an EEPROM or a flash ROM in the information recording medium driving means. In order to produce the identifier peculiar to the information recording medium driving means, therefore, hardware modification of the changer controller is never required, and it is requested only to apply small software modification on the data transfer which is to be implemented via a local bus line. In both the exterior and the interior of the changer, peculiar identifiers can be easily allocated to the information recording medium driving means, respectively. Even when plural changers are used in a large scale system, therefore, correspondence relationships between the electrical connection routes (access paths) to disk drives and element addresses which are used in the disk transportation to the drives can be surely constructed.
In a third aspect of the invention, the identifier contains a product serial number of the information recording medium driving means.
This configuration can attain the following effect in addition to the effects of the second aspect of the invention. Since the identifier is a product serial number of the information recording medium driving means, the identifier may be incorporated into the information recording medium driving means in the production process of the means. In this case, there are no identical serial numbers in all the products, and hence each of the information recording medium driving means can be most surely identified.
In a fourth aspect of the invention, the first controlling means gives to incorporated information recording medium driving means the identifier corresponding to an element address of the incorporated information recording medium driving means, and the information recording medium driving means stores the given identifier.
This configuration can attain the following effect in addition to the effects of the first aspect of the invention. It is not necessary to previously store the peculiar identifiers in the information recording medium driving means. Therefore, the information recording medium driving means are not required to have a nonvolatile memory for storing the identifier.
In a fifth aspect of the invention, the changer controller and the information recording medium driving means are connected to a SCSI controller to which a SCSI bus can be connected.
This configuration can attain the following effect in addition to the effects of the first to fourth aspects of the invention. Even when the changer controller, the information recording medium driving means, and a computer system are connected to one another via SCSI busses, the computer system can correctly recognize correspondence relationships between the information recording medium driving means identified by a SCSI bus number and a SCSI ID, and the element addresses where the means are mounted, on the basis of the identifier which is peculiar to the information recording medium driving means and commonly contained in both sets of information respectively obtained through two routes.
In a sixth aspect of the invention, the first command is a read element status command which is defined in the SCSI standard.
This configuration can attain the following effect in addition to the effects of the fifth aspect of the invention. The read element status command which is defined in the SCSI standard is used as a condition for activating a control of transmission of the correspondence relationships from the changer controller to a computer system. Consequently, there is an advantage that necessary software modifications which are to be performed in the computer system and the changer controller can be minimized in degree.
In a seventh aspect of the invention, the second command is an inquiry command which is defined in the SCSI standard.
This configuration can attain the following effect in addition to the effects of the fifth or sixth aspect of the invention. The inquiry command which is defined in the SCSI standard is used as a condition for activating a control of transmission of the identifiers from the information recording medium driving means to a computer system. Consequently, there is an advantage that necessary software modifications which are to be performed in the computer system and the information recording medium driving means can be minimized in degree.